Dust destruction and survival in the Cassiopeia A reverse shock

Abstract

Core-collapse supernovae (CCSNe) produce large ($\gtrsim 0.1{\mathrm{M}}_{\odot }$) masses of dust, and are potentially the primary source of dust in the Universe, but much of this dust may be destroyed before reaching the interstellar medium. Cassiopeia A (Cas A) is the only supernova remnant where an observational measurement of the dust destruction efficiency in the reverse shock is possible at present. We determine the pre- and post-shock dust masses in Cas A using a substantially improved dust emission model. In our preferred models, the unshocked ejecta contains $0.6-0.8{\mathrm{M}}_{\odot }$ of $0.1\hat{\mathrm{I}}¼\mathrm{m}$ silicate grains, while the post-shock ejecta has $0.02-0.09{\mathrm{M}}_{\odot }$ of $5-10\mathrm{nm}$ grains in dense clumps, and $2\times 10^{-3}{\mathrm{M}}_{\odot }$ of $0.1\hat{\mathrm{I}}¼\mathrm{m}$ grains in the diffuse X-ray emitting shocked ejecta. The implied dust destruction efficiency is $74-94\%$ in the clumps and $92-98\%$ overall, giving Cas A a final dust yield of $0.05-0.30{\mathrm{M}}_{\odot }$. If the unshocked ejecta grains are larger than $0.1\hat{\mathrm{I}}¼\mathrm{m}$, the dust masses are higher, the destruction efficiencies are lower, and the final yield may exceed $0.5{\mathrm{M}}_{\odot }$. As Cas A has a dense circumstellar environment and thus a much stronger reverse shock than is typical, the average dust destruction efficiency across all CCSNe is likely to be lower, and the average dust yield higher. This supports a mostly-stellar origin for the cosmic dust budget.

10 pages, 9 figures, MNRAS accepted